Ryoibi 720r String Trimmer Won't Start


Old 10-11-08, 11:11 AM
Thread Starter
Join Date: Oct 2008
Location: Buffalo Grove, IL
Posts: 4
Ryoibi 720r String Trimmer Won't Start

I have owned the Ryobi 720r string trimmer for about 15 years and it has always been excellent in starting and running well. Just recently it started giving me trouble starting. I dismanteled the carborator completely and blew out all the orfices and it seemed to help - was hard to start but was able to run. It worked for about 1 month and then the same thing happened. This time I took the carborator apart again including the floating needle valve that is attached to a spring type lever (I had missed this last time). I also took out the spark plug, checked the gap and dried it off. When I use starting fluid (ether), it runs for about 3 seconds but won't run on the fuel. It's got a spark and I assume compession so my guess is something is wrong with the carborator.

Any ideas on what to try next?
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Old 10-11-08, 01:36 PM
Join Date: Jun 2006
Location: St. Louis
Posts: 2,365
I would suggest checking/replacing the fuel lines and in tank filter, also check for a cracked/leaking primer bulb. Have a good one. Geo
Old 10-23-08, 03:58 PM
Join Date: Oct 2008
Location: Florida
Posts: 2
Connect Fuel Line

My Fuel line broke on my Ryobi 725 string trimmer and I purchased a new filter and line assembly but I now if fuel form the filter goes to the top or bottom of the carburator. Can you help me?
Old 10-23-08, 04:02 PM
Join Date: Oct 2008
Location: Florida
Posts: 2
The primer bulb is ok , Ihave the manual but it dosen't show how to connect fuel lines
Old 10-23-08, 08:14 PM
cheese's Avatar
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Join Date: Jul 2001
Location: USA
Posts: 16,814
Did you install a kit in the carb when you had it apart? Did you install the diaphragm right side up?

I believe the fuel line with the filter will go to the fitting nearest to the side of the carb with 1 or 2 screws holding the cover on (depending on the carb brand), not the side with 4 screws.
Old 10-26-08, 02:32 AM
bigfred's Avatar
Join Date: Sep 2006
Location: USA
Posts: 418
I had a similar problem with a Weedeater blower. Turned out to be a compression problem. Don't recall the exact details; but I think it was leaking compression both where crankshaft was connected to the impeller, and where carburetor connected to engine. I ended up buying a new one due to cost to repair.

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